Connection units are currently known which are provided with an insert having two parts the front or back part of which is provided with metallic or plastic retaining clips for maintaining electric contacts in said insert. Both parts of the insert are generally stuck together for preventing any separation of the unit and for electrically isolating each electric contact.
The presence of such retaining clips in a two-part insert increases the overall dimension for each contact in the insert and the maximal contact density in a given insert volume is limited. Moreover, the presence of these retaining clips, which are most of the time made of a metallic material, generates electric losses which reduce the voltage behavior of such a connection unit.
Connection units are also known which are provided with a monobloc insert, i.e. in one piece, in which the electric contacts are maintained by forcing them into the insert, and the material flexibility of which enables such a deformation that the so-mounted contacts are blocked therein. The realization of such a connection unit is relatively simple, since the insert is formed of one piece, generally molded, and has only few pieces to be assembled.
Until now, the inserts used are exclusively intended to receive only one sort of contacts, i.e. either contacts which are forced into a monobloc insert or contacts which are maintained by a clip in a two-part insert. When one desires to use at the same time forced-mounting contacts and contacts with a retaining clip, which have various properties and advantages, it is now necessary to use two different connection units each having one type of contacts, which needlessly increases the costs and the overall dimension at the electric connection zone.